ew928

Ya figgur that WOT would be something that the Stuttgart enginmineers would get right as that right lane on the Autobahns would give the full throttle position lots of excercise.

Damn leaking electrons.

Louie928

Or, switch on the NOS at some throttle opening point.

derporsche928

Helo John,
Just trying to share..... and even a blind squirrel finds a nut sometimes.....
FWIW, the way I've found to best check for this poor connection now, is to clip on test leads to the connectors and then flick the switch around the black plastic joint area with your finger and note whether you lose continuity or resistance jumps around..... (and trust me, you will, or at least I have on any that are even remotely suspect...)
Then do the same check with your leads connected to the contact strips on the inboard side of the black plastic, and you will discover contact nirvana.....
Best,

Bill Ball

My switch is practically new, but I will look at it when I remove the intake for SC reinstallation. I can't see any wear in the linkage to account for the loss of WOT, or rather, it's inability to trip except right at the extreme end of the throttle plate travel.

derporsche928

Hello Bill,
Out of the three failures I've seen, one was on a brand-spanking new switch, and one was very near new....... I know I was PO'd when the new one was bad, as it's pretty frustrating to do the intake thingy, only to find a dis-functional NEW part.....
Check yours as I've described above and I'd bet it's this same failure mode I've described......
As far as your tripping only near the end of the throttle, I'd bet this poor design is also the culprit here, as the contacts are likely fine on your switch, but the butt connection under the plastic is only made with the pressure of the flexy strip pushed that way......
(I know this may look like a pretty lame excuse for an explanation, but I'd still put my money on it all being related to this poorly designed butt-connection thingy as I'd described above, and there is really no adjustment or anything to wear to cause the effect of only getting the signal that far open as you describe.)

Best Regards,

Bill Ball

Greg: Thanks for the further explanation of how the butt connections might have made the switch work the way it is working.

derporsche928

Bill,
Your posts have always helped me, so I'm just happy if I can give your big brain something to wrap around occasionally too ..... I know you'll get to the bottom of it..... Let me know what you find.....

John Speake

I looked again at those horrible solder WOT joints, and found that in fact both of them have come apart !

It is strange that the closed throttle switch, with similar connections has not (and don't usually ?) failed.

derporsche928

Hey John,... Yep, from what I remember, (don't happen to have one open in front of me they looked like they just butted the two metal strip ends together and molded them in the plastic with little, if any, solder....
As someone said here already,..... definitely not one of Bosch's finer engineered pieces.....
In fact, I'd be tempted to solder a NEW one before I put it on in the future....
Best,

John Speake

Hi Greg
Yes, they are butt joints. It's difficult to see of the sloder or the plating has fractured. The two WOT springs are held into a plastic clamp which appears to be glued onto the main body of the unit.

This looks good and firmly fixed. But there has to have been some strain (thermal) applied to pull those two soldered joints apart.

It is strange that the contacts from the idle microswitch also result in the same type of soldered butt joint.

I had quite a job removing the cover from the switch I have. It was very firmly glued all around with a reasonable overlap. I have to hacksaw it off ......

I see in another thread today that JPRodkey used your "keyhole surgery" technique to fix a problem with his WOT switch.

derporsche928

Hello John....
I've luckily been able to get them apart at their seams, but I'd be tempted to glue the one you cut open, and keep for a spare regardless......
Took me a minute to find JP's thread you referenced, and I just clarified this there.....
I don't know how to put the link here, but you obviously know the one..... (90' Idle or something)

I have seen one idle micro switch cold solder joint failure right there at the visible joint, but the failures I've seen on the WOT are not the visible soldered connections you can see, but rather under the plastic where these strips have been butted end to end and then molded over.
You have to grind the plastic from off the top of the strips to see this..... Is that what you are seeing?
I don't know if I described that clearly enough before, and thought I'd better check to be sure....
(Sometimes this typing rather than talking can be cumbersome, and my dang "t" key on this computer needs a good pounding to work right....)
Best Regards,

John Speake

Hello Greg
Well they say a pixture is worth a thousand words, so here's where the two failed joints are on my switch.

I don't quite understand where you mean "under the plastic" because as far as I can see the contact strips come straight through the plastic (rectangular) part before the soldered part....

derporsche928

Here's a pic of one I'd fixed and kept for a spare, but hadn't glued over the burr bit grooves yet.....

John Speake

Snap ! We both posted at the same time. So there is a joint under that plastic part ?

What a crap design !

JP Rodkey

Aha. So that's what you (Greg) meant by grinding away the material! Based on your picture, there doesn't appear to be a joint that's hidden inside the molded plastic contact arm support (the part you ground out). Of course, you actually saw it close up, so it's possible. If Bosch actually did that, I would love to know why - because there is no design or manufacturing reason I can think of that would need a joint buried in there. On the other hand, it makes sense that both contact arms are one solid piece, soldered only at the two posts clearly shown in John's pic above. If you soldered the area under the plastic, it would almost certainly melt/reset the solder at the joint shown in John's pic. As I wrote in my thread, that is the only place I put the solder gun and it apparently fixed it.